I'm running Windows 8 and xampp, and tried on Google Chrome and IE 9.
Completely blank install and fresh database.
Same errors as cdmein. The error appears when you try clicking on any link in the admin section, and nothing happens. If I right click > open in new window, it opens the page as expected. The front end is working fine.
Just a thought Ingo/Sean... could you maybe send me a working vanilla install of the scripts and db and i'll see if errors still occurs? Alternatively, I could give you FTP access to my server to upload...
Maybe we do it the other way around? You send me a ZIP of your working copy of SS, to ingo at silverstripe dot com.
In addition, it would be good to get web access to your local server, via dyndns or a similar service.